Anne Tromelin

Identification of Odorant-Receptor Interactions by Global Mapping of the Human Odorome

The human olfactory system recognizes a broad spectrum of odorants using approximately 400 different olfactory receptors (hORs). Although significant improvements of heterologous expression systems used to study interactions between ORs and odorant molecules have been made, screening the olfactory repertoire of hORs remains a tremendous challenge. We therefore developed a chemical systems level approach based on protein-protein association network to investigate novel hOR-odorant relationships. Using this new approach, we proposed and validated new bioactivities for odorant molecules and OR2W1, OR51E1 and OR5P3. As it remains largely unknown how human perception of odorants influence or prevent diseases, we also developed an odorant-protein matrix to explore global relationships between chemicals, biological targets and disease susceptibilities. We successfully experimentally demonstrated interactions between odorants and the cannabinoid receptor 1 (CB1) and the peroxisome proliferator-activated receptor gamma (PPARγ). Overall, these results illustrate the potential of integrative systems chemical biology to explore the impact of odorant molecules on human health, i.e. human odorome.

Retention/release equilibrium of aroma compounds in fat‐free dairy gels

BACKGROUND The replacement of fat by thickeners in fat-free yogurts leads to an important modification of aroma compound partitioning, with an impact on aroma perception. Investigation of retention/release equilibria allows a good understanding of aroma compound behaviour depending on food composition. RESULTS Vapour/liquid equilibria of ten aroma compounds (two esters, two ketones, three aldehydes and three alcohols) in several media were studied to investigate the influence of pectin addition to fat-free dairy gel on the retention/release equilibrium. The partition coefficient of each aroma compound was measured by headspace analysis at equilibrium in six media (pure water, low-methoxylated pectin gels and dairy gels with or without added pectin). The release of aroma compounds was similar in the aqueous media (pure water and pectin gels) on the one hand and in the dairy gels on the other hand. However, a trend to greater release occurred with the addition of pectin in both cases. Four aroma compounds were more retained in dairy gels than in water and pectin gels. No relationship appeared between retention and either the chemical function or hydrophobicity (logP values) for the entire set. However, several subsets showed a linear correlation between K and logP values. CONCLUSION These results suggest that other structural properties than hydrophobicity are probably involved, changing the retention/release behaviour of aroma compounds according to the matrix composition. In order to probe the interactions, further experiments with a larger set of aroma compounds followed by molecular modelling interpretation are needed.

Proposed alternative phase ratio variation method for the calculation of liquid-vapour partition coefficients of volatiles.

The phase ratio variation PRV method is a classical way to determine the partition coefficients of volatile compounds between their solution and vapour phases in a variety of circumstances. However, some results obtained by this method can be disappointing. A new PRV equation in which the initial liquid-phase solute concentration is replaced by the liquid-phase solute concentration at equilibrium is proposed. This proposed PRV equation is a second-order polynomial equation. To thoroughly examine the possible modes of calculation, noisy dummy data were generated using both the classical, first-order PRV model (PRV(1)) and the proposed, second-order model (PRV(2)). Thus, pseudo-data obtained from simulations were compared to published experimental data. We observed that the second-order model, PRV(2), produces a lower variability, allowing improved K precision. Moreover, the obtained K(PRV(2)) values are very close to those obtained by classical equilibrium headspace analysis (EHSA). The PRV(2) model we propose responds to the demand for a simple, reliable method and is a useful alternative for the calculation of liquid-vapour partition coefficients.

Influence of the Parameters Molecular Structure and Granularity on the Compactibility of a Powder

AbstractThe aim of this study was to determine whether it is possible to obtain better characterization of materials in order to find out if these one are suitable in Quality Assurance for direct tableting. We tried to show that a methodological approach combining chemical, physical and technological aspects could control the direct compression process. We chose orthoboric acid as a study model for the direct compression. From a chemical point of view, our findings show only one crystalline molecular structure (RX, DSC and Pycnometry) which means an homogeneous chemical system. Concerning the particular state (Sieving and Microscopic approach), granularity is very different between the two forms, “crystalline” ABC and “powder” ABP.Technological studies show a rheological and mechanical difference, as it is demonstrated, on the one hand by the behaviour of the bulk powder (Volumenometer), on the other hand by the feasibility on the machine (Alternative EKO). We explain this difference of behaviour by only ...

LES RÉCEPTEURS OLFACTIFS ET LE CODAGE DES ODEURS

Resume La premiere etape de la detection olfactive implique l’activation de recepteurs olfactifs par les molecules odorantes. Ces recepteurs sont des proteines membranaires contenues dans la membrane des cils portes par les neurones sensoriels olfactifs localises dans l’epithelium olfactif. Le codage de l’odeur resulte de l’activation combinatoire d’un ensemble de recepteurs et repose sur leur expression clonale. La connectique neuronale aboutit a la formation, dans le cortex, d’une image sensorielle olfactive qui est percue consciemment en tant qu’odeur. Ce systeme combinatoire permet, avec seulement environ 340 recepteurs differents, de discriminer des myriades de molecules odorantes naturelles ou non (nouvelles flaveurs culinaires, molecules de synthese, etc.). L’extreme diversite des genomes olfactifs chez l’etre humain peut contribuer a expliquer des differences de comportements alimentaires.

Relationship Between Particle Size and Dissolution Rate of Bulk Powders and Sieving Characterized Fractions of two Qualities of Orthoboric Acid

AbstractWe have carried out a study of the particle size distribution and aqueous dissolution rate of two commercially available qualities of orthoboric acid, labeled “crystal” (ABC) and “powder” (ABP). In a previous work, we have shown that the two commercial qualities of orthoboric acid chosen as model compound (“powder” and “crystal”) are related to the same crystal network in spite of their dvferent names. However, these two qualities have very different size particle distributions, as previously determined by sieving and confirmed by the present laser light scattering study. Dissolution testing is performed under sink conditions and show that the bulk ABC quality dissolves far more rapidly that the bulk ABP quality, For each quality, dissolution rates of four sieved particle size fractions (0-90 μm; 90-125 μm; 125-180 μm; 180-250 μm) were compared. Concerning the ABC quality, comparisons were also done with three other particles size fractions: 250-355 μm, 355-500 μm, and 500-710 μm. This study used ...

Prediction of perception using structure–activity models

Abstract This chapter presents the structure–activity relationships approaches that could be applied to the understanding of flavor perception, and ultimately to lead to their prediction. The chapter involves two main parts: the methods and the requirements for the proper implementation of the quantitative structure–activity approach are presented in the first part; the second part is devoted to the studies already realized on aroma compounds, and that have been applied to the main issues governing the aroma perception: the release in vapor phase, the intensity of perception, and the link between molecular structure and odor quality.

Improvement of Partition Coefficients Determination of Aroma Compounds in Food Matrices by the Phase Ratio Variation Method

The Phase Ratio Variation (PRV) method is a very valuable method commonly used for liquid/vapor partition coefficients data acquisition of aroma compounds. Nevertheless, there are some limitations to this method, especially for volatile compounds. A careful examination of the PRV equation leads us to propose the following expression: 1/C vap-real = ( n liq /n 0 ) × 1 /C vap-ideal = ( n liq /n 0 ) × ( 1 /KC 0 + ( 1 /C o ) β ) We performed an examination for two cases of K values (K1=0.001 and K2=0.05), highlighting that a careful choice of β range values is crucial in the reliability of the regression calculation 1/A versus β.